Study of Near-Sonic Flows

对近声速下的流动进行了数值和实验研究。以下是本研究得到的主要结果。TAS-code是一种基于内部非结构网格的CFD软件，它是一种分析和设计跨声速飞机的实用工程工具。开发了一种基于伴随方程的高效直接优化程序。将其应用于某跨音速飞机机翼-吊舱-塔架一体化优化，获得了重要的工程信息。利用遗传算法和数据挖掘方法，开发了一种高效、多学科的跨声速飞机优化设计程序。提出了一种利用CFD提高阻力预测精度的新方法。利用这种方法，可以对求解精度非常敏感的小波进行优化。利用TAS-code对一架速度为0.98马赫的音速飞机进行了空气动力学优化。结果表明，提高了25%的升阻比，并获得了高效音速飞机的一般条件的重要知识。对返回舱在跨声速时的动态不稳定趋势进行了数值分析，提出了返回舱动态稳定性的预测方法。采用LES/RANS混合方法对高速车辆基流的物理特性进行了数值研究。结果表明，跨声速时的时间序列特征与其他速度区有显著差异。利用TAS-code对可重复使用航天飞机近声速升降副翼反转现象进行了数值研究，并找出了原因。提出了防止升降角反转的方法。对弱激波的各种流动现象进行了实验和数值研究，以加深对其物理认识。

Numerical and experimental studies of flows at near-sonic speed have been conducted. The following are the major results obtained by this research.1. The TAS-code, an in-house unstructured-grid based CFD soft, was sophisticated and a practical engineering tool for analyzing and designing transonic airplanes was constructed.2. An efficient direct optimization code using the adjoint equation was developed. It was applied to optimize the wing-nacelle-pylon integration of a transonic airplane and an important engineering information was obtained.3. An efficient, multi-disciplinary optimization code for designing a high-performance transonic airplane was developed using the genetic algorithm and the data mining method.4. A new method to improve the prediction accuracy of the drag by CFD was developed. With this method, an optimization of winglet, which is generally very sensitive to the solution accuracy, becomes possible.5. A sonic plane at Mach 0.98 was aerodynamically optimized using the TAS-code. The result showed 25% improvement of the lift-to-drag ratio and the important knowledge of a general condition for an efficient sonic plane was obtained.6. Dynamically unstable tendency of a reentry capsule at transonic speed was numerically analyzed and a prediction method for the dynamic stability of the capsule was proposed.7. Physics of base flows of a high-speed vehicle was numerically investigated with the LES/RANS hybrid methodology. It was shown that the time-series characteristics at transonic speed was significantly different from other speed regimes.8. An elevon reversal phenomena at near-sonic speed of a reusable space plane was numerically investigated using the TAS-code and the cause was identified. The method to prevent the elevon reversal was proposed.9. Various flow phenomena of weak shock waves were experimentally and numerically investigated for the physical understanding.